The present invention relates generally to systems and methods for three-dimensional mapping and reconstruction, and specifically to mapping and reconstruction of the interior of body organs, such as the heart.
Various methods of diagnostic imaging are known in the art. Methods used for imaging the heart, for example, include fluoroscopy, angiography, echocardiography, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission tomography (SPECT). Many of these methods produce three-dimensional (3D) image information, which can then be rendered for viewing in the form of parallel slices through the heart, or as a pseudo-3D display on a video monitor. In order to administer treatment, the treating physician must build a 3D picture in his or her mind based on the two-dimensional pictures that are displayed. The transposition is particularly tricky when therapy is to be administered inside the heart, such as local electrical ablation of aberrant electrical pathways, or laser myocardial revascularization.
It is also known in the art to map the heart using a mapping probe, typically a catheter, inside the heart chambers. Exemplary methods and devices for this purpose are described in U.S. Pat. Nos. 5,471,982 and 5,391,199 and in PCT patent publications WO94/06349, WO96/05768 and WO97/24981, whose disclosures are incorporated herein by reference. U.S. Pat. No. 5,391,199, for example, describes a catheter that includes both electrodes for sensing cardiac electrical activity and miniature coils for determining the position of the catheter relative to an externally-applied magnetic field. Using this catheter a cardiologist can collect data from a set of sampled points in the heart within a short period of time, by measuring the electrical activity at a plurality of locations and determining the spatial coordinates of the locations. Locations of the mapping catheter within the heart can be superimposed on a 3D reconstruction of an image of the heart, such as an ultrasound image, acquired prior to or during the catheter study. Color codes are used to represent electrical activity sensed by the catheter.
U.S. Pat. No. 5,738,096, whose disclosure is incorporated herein by reference, describes methods for geometrical mapping of the endocardium based on bringing a probe into contact with multiple locations on a wall of the heart, and determining position coordinates of the probe at each of the locations. The position coordinates are combined to form a map of at least a portion of the heart. Once the position of the catheter is known, external sensors can be used to provide local physiological values of heart tissue adjacent to the tip of the catheter. For example, if the catheter incorporates a radioactive marker suitable for SPECT, local functional information can be gleaned from a SPECT image. Yet another example is determining local perfusion from Doppler-ultrasound images of the coronaries, from nuclear medicine images or from X-ray or CT angiography, and overlaying the perfusion map on the geometrical map. The image of the catheter in the perfusion map can be used to align the perfusion map and the geometrical map. Alternatively, the alignment may be carried out using fiducial marks or anatomical reference locations, either automatically or manually.
Further methods for creating a three-dimensional map of the heart based on these data are disclosed, for example, in European patent application EP 0 974 936 and in a corresponding U.S. patent application Ser. No. 09/122,137 now U.S. Pat. No. 6,226,542 issued May 1, 2001, which is assigned to the assignee of the present patent application, and whose disclosure is incorporated herein by reference. As indicated in these applications, position coordinates (and optionally electrical activity, as well) are initially measured at about 10 to 20 points on the interior surface of the heart. These data points are generally sufficient to generate a preliminary reconstruction or map of the cardiac surface to a satisfactory quality. The preliminary map is preferably combined with data taken at additional points in order to generate a more comprehensive map.
It is an object of some aspects of the present invention to provide improved methods and apparatus for mapping and visualization of internal body structures, and particularly of the heart.
It is a further object of some aspects of the present invention to provide improved methods and apparatus for administering local treatment of pathological conditions within the heart.
In preferred embodiments of the present invention, a position-sensing catheter is used to generate a 3D geometrical map of the internal surface of a heart chamber of a subject. A 3D diagnostic image of the heart is captured in conjunction with generating the 3D map, typically either before or concurrently with the mapping. The image and map are brought into mutual registration, and diagnostic information from the image, such as perfusion information, is then marked on the 3D map, preferably in the form of color coding. Based on the combined diagnostic and geometrical information, a physician operating the catheter is able to identify and visualize areas of the heart that are in need of treatment, due to low perfusion, for example. The physician preferably uses the catheter to apply a local invasive therapy, such as laser revascularization, to specific points that are located using the color-coded 3D map. Alternatively, a local diagnostic technique, such as a biopsy, may be performed at such specific points.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a method for mapping a structure in a body of a subject, including:
capturing a three-dimensional (3D) image of the structure including diagnostic information;
generating a 3D geometrical map of the structure using a probe inserted into the structure;
registering the image with the map, such that each of a plurality of image points in the image is identified with a corresponding map point in the map; and
displaying the map, such that the diagnostic information associated with each of the image points is displayed at the corresponding map point.
In a preferred embodiment, the diagnostic information is related to blood flow in the structure, wherein the diagnostic information includes local perfusion data. In other preferred embodiments, the diagnostic information includes metabolic data, or is related to uptake of a substance in tissue of the structure, or is related to motion of the structure.
Preferably, generating the geometrical map includes bringing the probe into contact with the structure at a multiplicity of locations on the structure, and recording position coordinates of the probe at the locations, wherein recording the position coordinates includes determining the coordinates using a position sensor in the probe.
Preferably, registering the image with the map includes applying a transformation to at least one of the image and the map so that following the transformation, the image and the map have a common axis and a common scale. Further preferably, registering the image with the map includes dividing the image into a plurality of parallel planar slices, perpendicular to the axis and mutually spaced along the axis, wherein the plurality of image points are located in the slices. More preferably, registering the image with the map includes finding an axial coordinate of each of the slices and an angular coordinate of each of the image points located in each of the slices, and identifying each of the image points with the map point having the same axial and angular coordinates. Most preferably, the structure includes a wall defining a cavity, and identifying each of the image points with the map point includes finding, at the axial and the angular coordinate, the image point that is within a section of the wall.
Preferably, displaying the map includes coloring the map to reflect the diagnostic information.
In a preferred embodiment, the method includes performing a medical procedure on the structure guided by the diagnostic information displayed on the map. Preferably, performing the medical procedure includes using the probe to perform the procedure locally at locations selected on the geometrical map, and the method includes marking on the geometrical map the locations at which the procedure was performed. Additionally or alternatively, performing the medical procedure includes performing a therapeutic procedure, wherein the diagnostic information relates to local blood flow in the structure, and wherein performing the therapeutic procedure includes performing a procedure for improving the local blood flow. Alternatively, performing the medical procedure includes performing a diagnostic procedure.
Preferably, the structure includes a heart of the subject, and generating the geometrical map includes mapping an endocardial surface in a ventricle of the heart.
There is also provided, in accordance with a preferred embodiment of the present invention, apparatus for mapping a structure in a body of a subject, including:
an imaging device, adapted to capture a three-dimensional (3D) image of the structure including diagnostic information;
a probe, adapted to be inserted into the structure, so as to generate a 3D geometrical map of the structure;
a processor, coupled to the probe and to the imaging device, and adapted to register the image with the map, such that each of a plurality of image points in the image is identified with a corresponding map point in the map; and
a display, coupled to be driven by the processor to display the map, such that the diagnostic information associated with each of the image points is displayed at the corresponding map point.